1. Field of the Invention
This invention relates to systems for replacing clogged filter elements with fresh filter elements in forced air systems and the like.
2. Description of the Prior Art
It is common knowledge that the efficiency, and thereby the cost of operation, of forced air heating and cooling systems is greatly dependent upon the condition of the filters used in those systems for maintaining clean air. Often manual replacement of the filters is relied upon to insure their cleanliness. Therefore, a need has developed for an inexpensive, effective mechanism which may replace clogged filter elements with fresh filter elements without the need of manual intervention.
U.S. Pat. No. 2,848,064, issued Aug. 19, 1958, to Gregory et al, shows an automatic filter changing device wherein the rate of air flow through a filter is measured by a pressure switch and upon the rate of flow decreasing below a predetermined minimum, the motor is started to advance a roll of filter material to the next clean position. The advance of the material is measured by a cam which contacts and rolls with the advancing filter material for stopping the motor after a predetermined linear measurement has been attained. U.S. Pat. No. 3,552,098, issued Jan. 5, 1971, to Cochran, shows an air filter control arrangement wherein a differential pressure sensor senses the difference in pressure on opposite sides of a filter medium and causes a predetermined length of filter medium to be fed out from a supply roll upon the increase of the sensed difference in pressure reaching a predetermined level. The Cochran control includes a wheel which rides against the filter medium for measuring the length of medium removed from the supply roll.